Machine and track assembly for use therewith

ABSTRACT

A track assembly for a machine includes a track having inner track seals, a rotatable track engaging element such as an idler or drive sprocket and a contact interface for protecting the seals during guiding the track about the rotatable element. The contact interface may include sacrificial wear material on the rotatable element and sacrificial wear material on corresponding track links. The contact interface may have a configuration based on a location of the seals, and is adapted to inhibit wear of the track links in regions adjacent the seals. In another aspect, the contact interface is a guide interface.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional of U.S. patent application Ser.No. 12/888,542, now U.S. Pat. No. 8,172,342 B2, filed Sep. 23, 2010,which is a continuation of U.S. patent application Ser. No. 11/975,206,filed Oct. 18, 2007, now U.S. Pat. No. 8,100,483.

TECHNICAL FIELD

The present disclosure relates generally to machine track, and relatesmore particularly to a machine and associated track assembly having aunique interface design between track assembly components to protectinboard track seals from damage.

BACKGROUND

A wide variety of machines utilize tracks, commonly as ground engagingpropulsion elements, but also for other purposes such as torquetransmission and conveying. It is common for such tracks to include aplurality of rotatable track engaging elements, with the track formingan endless chain that is moved about the rotating elements duringoperation. The demands placed upon such machines and their associatedtrack assemblies can be quite substantial, and machine tracks are oftenrelatively robust to provide a long operating life despite significantmechanical stresses, strain and wear experienced during operation.

One conventional track system known from track-type tractors and thelike utilizes one or more rotatable idlers which engage the tracks,typically working in conjunction with a drive sprocket. The idlerspassively rotate to guide the associated track about a desired path. Itis common in conventional track systems for the rotatable idler to rollagainst “rails” located on links of the track chains. More recently,designs have been implemented in certain machines where the rotatableidler and track are configured such that the idler contacts the trackbetween adjacent parallel track chain assemblies, rather than riding onthe rails.

One such design is known from U.S. Pat. No. 5,829,849 to Lawson. In theLawson strategy, an idler contacts roller bushings located between trackchain assemblies to support and guide the track as it rotates to propelthe machine. Tapered side portions of the idler provide lateral guidingof the track chain assemblies. Lawson overcomes certain design andoperating issues associated with conventional systems where the idlerrides on rails. While Lawson provides a successful strategy, there isalways room for improvement, particularly with regard to the wearcharacteristics of the system.

The present disclosure is directed to one or more of the problems orshortcomings set forth above.

SUMMARY

In one aspect, a track assembly for a machine includes a track having afirst chain assembly, a second chain assembly coupled with the firstchain assembly via a track pin, and a first and second seal locatedwithin a first and second bore, respectively, of track links of thefirst and second chain assemblies. The track assembly further includes arotatable track engaging element configured to guide the track at leastin part by contacting the track between the chain assemblies, and acontact interface between the rotatable track engaging element and thetrack. The contact interface includes means, located on at least one ofthe track and the rotatable track engaging element, for inhibiting tracklink wear in regions adjacent the seals during contacting the track withthe rotatable track engaging element.

In another aspect, a machine includes a frame, and at least one trackcoupled with the frame which includes a first chain assembly and asecond chain assembly, the chain assemblies each including a pluralityof track links and being coupled together via a plurality of track pins.A plurality of seals are positioned within bores in the track links, andthe machine further includes a rotatable track engaging element havingan outer diameter contacting the track between the first chain assemblyand the second chain assembly. The machine further includes a contactinterface between the rotatable track engaging element and the trackwhich includes a contact element on at least one of the track and therotatable track engaging element which is configured to inhibit tracklink wear in regions adjacent to the seals during contacting the trackwith the rotatable track engaging element.

In still another aspect, a method of protecting seals of a machine trackduring operating the machine track includes the steps of moving amachine track having first and second parallel chain assemblies of tracklinks about a rotatable track engaging element, and guiding the machinetrack relative to the track engaging element at least in part bycontacting the track engaging element with the track between the firstand second chain assemblies. The method further includes a step of,during guiding the machine track, protecting inner track seals disposedwithin the track links at least in part by inhibiting contact betweenthe rotatable track engaging element and regions of the track linksadjacent the inner track seals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side diagrammatic view of a portion of a machine accordingto one embodiment;

FIG. 2 is a side elevational view of an idler suitable for use in themachine of FIG. 1;

FIG. 3 is a sectioned view taken along line 3-3 of FIG. 1;

FIG. 4 is a sectioned view taken along line 4-4 of FIG. 1;

FIG. 5 is a partial sectioned view taken along line 5-5 of FIG. 1;

FIG. 6 is a partial sectioned view of a track assembly according toanother embodiment;

FIG. 7 is a partial sectioned view of the track assembly of FIG. 6 takenin a different section plane;

FIG. 8 is a partial sectioned view of a track assembly according toanother embodiment;

FIG. 9 is a diagrammatic view of a portion of a track assembly accordingto another embodiment;

FIG. 10 is a partial sectioned view of a track assembly according toanother embodiment;

FIG. 11 is a partial sectioned view of a track assembly according toanother embodiment; and

FIG. 12 is a partial sectioned view of a track assembly according toanother embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a portion of a machine 10 accordingto the present disclosure. Machine 10 is shown in the context of atrack-type machine having a first ground engaging track 16, mounted at afirst side of a frame 12, and also including a second ground engagingtrack identical to track 16 and positioned at a second side of frame 12but not visible in FIG. 1. Track 16 extends about a plurality ofrotatable track engaging elements, including an idler 20 having an axisof rotation A, a drive sprocket 68 having an axis of rotation B and aplurality of track rollers, one of which is shown and identified viareference numeral 26. Machine 10 may also include other rotatable trackengaging elements coupled with each of its one or more tracks such as anadditional idler. While only a single track is shown in FIG. 1, thepresent description of track 16 and the track assembly 14 of which it isa part should be understood to refer also to a second track andassociated track assembly of machine 10. While machine 10 may be atrack-type machine such as a track loader, excavator, tractor or anothermobile machine, the present disclosure is not thereby limited. In otherembodiments, track assembly 14 might comprise a portion of a machinesuch as a conveyor. In all embodiments contemplated herein, trackassembly 14 will be configured such that certain types of wear, inparticular wear affecting track seals as described hereinbelow, will bereduced or eliminated as compared with conventional designs.

Track 16 will typically comprise two parallel track chain assemblies,one of which is shown in FIG. 1 and identified with reference numeral 18b, extending in parallel and coupled together via a plurality of trackpins 28. In the illustrated embodiment, track chain assembly 18 bconsists of a plurality of straight outboard track links 22 alternatingwith a plurality of straight inboard track links 24, although othertrack configurations such as those having S-shaped links or multi-piecelink assemblies are contemplated herein.

During moving track 16 about idler 20, inboard links 24 mayintermittently or continuously contact idler 20, guiding track 16thereabout. Each inboard link 24 may have a contact length L with idler20, the significance of which will be apparent from the followingdescription. Links 24 will also tend to contact sprocket 68 duringmoving track 16 thereabout, and the present description emphasizingidler 20 should be understood to be similarly applicable to aninteraction between sprocket 68 and track 16, except as otherwiseindicated. Referring also to FIG. 2, there is shown a side view of idler20 showing axis of rotation A, an outer diameter 34 or outer diametersurface, which is positioned at a constant radial distance from axis A,and an inner diameter 95 or inner diameter surface. In the embodimentshown, outer diameter 34 is configured to contact track 16 between itsrespective chain assemblies, in particular contacting track pins 28, orrotating bushings positioned on track pins 28, as further describedherein. In other embodiments, a different engagement strategy betweentrack 16 and idler 20 might be used, for example, a sprocketed idlercould be used. Idler 20 further includes a step 32 spaced radiallyinwardly of outer diameter 34 and separated from outer diameter 34 via atransition surface 33 which is an outboard surface. Transition surface33 extends a first radial distance from a seal protecting wear surface43 b to outer diameter 34. An inboard surface 97 extends a second,greater radial distance from seal protecting wear surface 43 b to innerdiameter 95. In connection with idler 20, the terms “inboard” and“outboard” mean, respectively, toward inner diameter 95 and away fromouter diameter 34, and toward outer diameter 34 and away from innerdiameter 95. Step 32 extends/protrudes axially from an axial side 30 ofidler 20, axial side 30 extending in a radial direction from innerdiameter 95 to outer diameter 34. Step 32 assists in mitigating wear intrack assembly 14 during operation, as further described herein. It mayfurther be noted from FIG. 2 that step 32 includes concentric radiallyinward and radially outward step edges 103 and 101, respectively, whicheach define a circle centered on axis A, and that transition surface 33adjoins outer diameter 34 at a corner 100. An opposite axial side ofidler 20 is not visible in FIG. 2, but will typically be substantiallyidentical to axial side 30.

Referring now to FIG. 3, there is shown a sectioned view taken alongline 3-3 of FIG. 1. As illustrated in FIG. 3, outer diameter 34 of idler20 contacts a rotating bushing 25 positioned about pin 28. In theillustrated embodiment, pin 28 comprises a cartridge pin having a fluidcavity 39 sealed via a plug 47. Pin 28 may further include inboardcollars 50 positioned on opposite sides of rotating bushing 25, andoutboard collars 52 positioned outboard of each inboard collar 50, andcoupled with pin 28 via any suitable means such as snap rings or thelike. In other embodiments, a pin configuration or a pin assemblydifferent from that illustrated in FIG. 3 might be used, such as a pinhaving an integral bushing, or a pin assembly other than a cartridgepin. Track chain assembly 18 b, including an inboard link 24 b and anoutboard link 22 b is positioned on pin 28, as is another track chainassembly 18 a, also including an inboard link 24 a and an outboard link22 a. Each of inboard links 24 a and 24 b includes a bore 46 a and 46 b,respectively, which is typically press fit with inboard collars 50. Afirst inner track seal 54 a and a second inner track seal 54 b arepositioned within collars 50, and thus positioned within bores 46 a and46 b, respectively. Exposed seal regions 105 of links 24 a and 24 b facea track guiding space 107. Lubricating fluid from cavity 39 may bedistributed to various of the components of track 16, and fluidly sealedfrom escaping via seals 54 a and 54 b, and such other seals as may beused in conjunction with outboard collars 52. Each of track chainassemblies 18 a and 18 b may further include a rail 23 upon which otherrotatable track engaging elements such as track roller 26 ride duringoperation.

It has been discovered that in certain conventional track assemblydesigns, rotatable components such as idlers and drive sprockets canhave a tendency to wear away material from inboard track links,eventually exposing and damaging inboard track seals and causing leaksof lubricating fluid, as well as potentially damaging the track. Thisphenomenon tends to result at least in part from the shape of the trackassembly components in regions where they have a tendency to contact oneanother. The present disclosure provides unique strategies forinhibiting this type of wear, and in particular includes a first contactinterface 40 a and a second contact interface 40 b, which inhibit tracklink wear in regions of the track links adjacent seals 54 a and 54 b.

In one embodiment, seals 54 a and 54 b may be protected fromwear-related damage at least in part by placing seals 54 a and 54 bwithin recesses 60 of contact interfaces 40 a and 40 b. It may be notedfrom FIG. 3 that ends of roller bushing 25 extend into recesses 60 inlinks 24 a and 24 b. The illustrated configuration can assist ininhibiting wear of regions of track links 24 a and 24 b adjacent seals54 a and 54 b, respectively, by positioning seals 54 a and 54 brelatively further from idler 20. It should be appreciated that over thecourse of many hours of operation, components such as bushing 25 canwear away, such that idler 20 can actually migrate closer to seals 54 aand 54 b than that which is shown in FIG. 3. Recessing seals 54 a and 54b can prevent or delay a time at which idler 20 wears material of links24 a and 24 b and begins to impinge on seals 54 a and 54 b. Moreover, insome embodiments using recesses 60 to protect seals 54 a and 54 b may bethe sole means for inhibiting track link wear in regions adjacentthereto, whereas in other embodiments recesses 60 might be used inconjunction with other means for inhibiting track link wear, or mightnot be used at all.

In certain embodiments, with or without using recesses 60, contactinterfaces 40 a and 40 b may be understood as “wear” interfaces whichdirect wear between element 20 and chain assemblies 18 a and 18 bpredominantly to areas of links 24 a, 24 b other than regions adjacenttrack seals 54 a and 54 b. For example, regions of track links 24 a and24 b where recesses 60 are disposed in the FIG. 3 version may beunderstood as “adjacent to” seals 54 a and 54 b as the term “adjacentto” is intended to be understood herein. In other embodiments, describedhereinbelow, contact interfaces of a track assembly may comprise guideinterfaces, which, rather than directing wear, inhibit or limit certaintypes of contact between the respective components in the first place.By designing track assembly 14 in the manner described herein, wear oninboard track links 24 a and 24 b in regions adjacent seals 54 a and 54b, respectively, can be reduced or eliminated as compared withconventional designs. In one embodiment, each contact interface 40 a and40 b may include sacrificial wear material 42 a and 42 b, respectively,located on idler 20, as well as sacrificial wear material 44 a and 44 blocated on inboard track links 24 a and 24 b, respectively. In otherembodiments, sacrificial wear material might be located on only one oftrack 16 and element 20. As mentioned above, idler 20 may include a step32 b on a first axial side 30, and another step 32 a on an oppositeaxial side 31, comprising portions of contact interfaces 40 a and 40 b.Each of steps 32 a and 32 b may protrude in axial directions relative tosides 31 and 30, respectively, and be spaced radially inwardly of outerdiameter 34.

In one embodiment, each of contact interfaces 40 a and 40 b may comprisea first planar face 43 a and a second planar face 43 b located on steps32 a and 32 b, respectively, each of which comprises a seal protectingwear surface also identified via reference numerals 43 a and 43 b, andincluding wear material 42 a and 42 b. Contact interfaces 40 a and 40 bmay also include a third planar face 45 a and a fourth planar face 45 blocated on track links 24 a and 24 b and including sacrificial wearmaterial 44 a and 44 b, respectively. Planar faces 43 a, 43 b, 45 a and45 b may be oriented perpendicular axis A of idler 20 such that acontact length L between links 24 a and 24 b and idler 20 comprises aplanar interface. The respective planar faces of the wear interfaces mayface toward one another, in opposed directions, at all locations whereidler 20 and links 24 a and 24 b may come into contact during operation,and may be parallel. This configuration can eliminate or reduce contactbetween edges or corners of idler 20 and portions of links 24 a and 24b, as may occur where an idler having tapered axial surfaces is used. Inother embodiments, certain of which are described herein, non-planarfaces of wear material may be used.

In one embodiment, wear material 42 a and 42 b and wear material 44 aand 44 b may consist of hardened forged or cast material of idler 20 andinboard track links 24 a and 24 b, respectively. Wear material 42 a, 42b, 44 a and 44 b may consist of the forged material of the respectivecomponents which is hardened by heat treating. In other embodiments,induction hardening, coatings or some other hardening strategy might beused. In FIG. 3, reference numeral 45 identifies forged material ofinboard track links 24 a and 24 b. It will often, though notnecessarily, be desirable to avoid hardening material of inboard tracklinks 24 a and 24 b in regions where bores 46 a and 46 b are located, toavoid interfering with press fits with inboard inserts 50. To this end,unhardened material 45 of each link 24 a and 24 b may define bores 46 aand 46 b.

Turning now to FIG. 5, there is shown a partial sectioned view takenalong line 5-5 of FIG. 1. As mentioned above, drive sprocket 68 may havea configuration having certain similarities with that of idler 20 toaddress similar wear concerns with respect to track 16. Sprocket 68 mayinclude a plurality of outer track contacting segments 70, one of whichis shown, each including a plurality of teeth 72 alternating with aplurality of pockets 74. It should be appreciated that in the FIG. 5illustration, tooth 72 is positioned forwardly of the section plane andis therefore shown in phantom. It may also be noted from FIG. 5 thatpocket 74 engages with rotating bushing 25 between the respective trackchain assemblies.

A first contact interface 140 a and a second contact interface 140 b maybe positioned on opposite axial sides of sprocket 68, and each mayinclude wear material 80 a and 80 b located on sprocket 68 and wearmaterial 44 a and 44 b located on inboard track links 24 a and 24 b.Interfaces 140 a and 140 b may each have a configuration based at leastin part on a location of seals 54 a and 54 b within their correspondingtrack links, similar to wear interfaces 40 a and 40 b associated withidler 20. In other words, by providing a particular shape for theinterfacing components, based on a location of the seals to beprotected, wear can predominantly occur in regions not adjacent to thesubject seals. For instance, in the case of sprocket 68 and idler 20,they are each configured via wear interfaces having wear material of anappropriate shape and location such that material is worn away fromlinks 24 a and 24 b predominantly in regions relatively closer to rails23, avoiding wear relatively closer to seals 54 a and 54 b.

“Guide” interfaces, as further described herein, may also be used inconnection with sprocket 68, rather than the illustrated wear features.In one embodiment, sprocket 68 may include a hub portion 76 having trackcontacting segment 70 coupled therewith via a plurality of bolts 82. Inother embodiments, rather than plural track contacting segments,sprocket 68 might consist of a single cast or forged piece, or one trackcontacting portion coupled with a separate hub portion. A nut strip 78or the like may be provided which receives a threaded end of each ofbolts 82. In FIG. 5, nut strip 78 is shown diagrammatically as a singlepiece, but may include a plurality of segments corresponding to aplurality of track contacting segments 70. In one embodiment, wearmaterial 80 a may be positioned on nut strip 78, at a first axial sideof sprocket 68, whereas other wear material 80 b may be positioned on anopposite axial side of sprocket 68, comprising a portion of segment 70.It will be noted that the configuration of nut strip 78 and segment 70is at least generally analogous to steps 32 a and 32 b of idler 20, eachof elements 78 and 70 having a planar face 143 a and 143 b whichcomprises a portion of the corresponding contact interface 140 a and 140b, respectively.

Turning now to FIG. 6, there is shown a track assembly 214 according toyet another embodiment. Track assembly 214 includes a rotatable trackengaging element 220, such as an idler, having a first axial side 231and a second axial side 230. Rotatable track engaging element 220 isconfigured to contact a track 216 between a first track chain assembly218 a and a second track chain assembly 218 b. Track assembly 214further includes a first contact interface 240 a between element 220 andchain assembly 218 a, and a second contact interface 240 b betweenelement 220 and track chain assembly 218 b. Contact interfaces 240 a and240 b may include a first step 232 a and a second step 232 b,respectively, positioned to extend from first and second axial sides 231and 230 and spaced radially inward of an outer diameter 234 of element220, and each including sacrificial wear material thereon. Theembodiment shown in FIG. 6 has certain similarities with previouslydescribed embodiments, in that contact interfaces 240 a and 240 b maycomprise wear interfaces whereby damage to inner track seals 54 a and 54b is inhibited via the proper placement of wear material, having anappropriate shape, which is based at least in part on a location oftrack seals 54 a and 54 b within their corresponding track links. Inother words, like the embodiment of FIG. 3 the embodiment shown in FIG.6 can include sacrificial wear material which wears away as track chainassemblies 218 a and 218 b are moved about element 220, avoiding wear inregions of the corresponding track links adjacent track seals 54 a and54 b. In one embodiment, each of steps 232 a and 232 b may have aconical face 243 a and 243 b, respectively, which includes sacrificialwear material, whereas each of the inboard track links 224 may includean opposed face 245 a and 245 b, respectively, which is configured tocontact faces 243 a and 243 b, respectively, during operation of trackassembly 214.

Track assembly 214 differs from track assembly 14 described above inthat, rather than each contact interface including an interface ofplanar surfaces, faces 243 a and 243 b may be conical, and disposed atan angle relative to an axis of rotation of element 220, rather thanbeing perpendicular thereto as in track assembly 14. Faces 245 a and 245b may be conical, planar or some other configuration. Referring also toFIG. 7, there is shown a sectioned view of track assembly 214 taken in adifferent section plane, at a location spaced from pin 28 in contrast toFIG. 6 which is sectioned approximately through the middle of pin 28.

Referring now to FIG. 8, there is shown another track assembly 314. Itshould be appreciated that track assembly 314 might be used with orcomprise a part of one of the other track assemblies described herein,and is thus not necessarily a separate system. Track assembly 314 mayinclude a rotatable track engaging element 368, such as a drivesprocket, having a flange 376 which is coupled with at least one trackcontacting segment 370 having alternating teeth 372 and pockets 374.Sprocket 368 operates generally in a manner similar to that describedabove with regard to the embodiment of FIG. 5, but has certaindifferences. Sprocket 368 is configured to engage with a track having afirst track chain assembly 318 a and a second track chain assembly 318b, and contacts the corresponding track between chain assemblies 318 aand 318 b, track contact segment 370 functioning in a manner similar tothat of the embodiment of FIG. 5 to apply driving force to theassociated track. A nut strip 378 may be bolted to flange 376, and incertain embodiments could include a plurality of separate nut strips.Nut strip 378 comprises a portion of a contact interface 340 betweendrive sprocket 368 and chain assemblies 318 a and 318 b. In contrast tothe embodiment of FIG. 5, nut strip 378 may include a conical face 343which is configured to contact another face 345 on links of chainassembly 318 b. An additional contact interface having a configurationsimilar to that of interface 340, to protect seals within track chainassembly 318 a, might be located on a side of sprocket 368 opposite thatof interface 340 in certain embodiments.

Referring to FIG. 9, there is shown a diagrammatic view of a trackcontacting segment 470 suitable for use with a track engaging elementsuch as a toothed idler or drive sprocket. Track contacting segment 470may include an arcuate body 471 having a plurality of teeth 472alternating with pockets 474, and is configured to engage with a trackin a conventional manner. Arcuate body 471 further includes an outerdiameter surface 434, an inner diameter surface 431 defining a segmentof a circle C having a center axis Z, a first axial side 430, a secondaxial side 431, and a plurality of apertures 440 communicating betweenaxial sides 430 and 431. An outboard axial surface 433 is shown locatedon axial side 430 in FIG. 9. Track contacting segment 470 furtherincludes a contact interface 440 which comprises a discontinuous contactinterface wherein faces of wear material 432 are spaced apart ratherthan consisting of a continuous step or the like. Identical wearmaterial faces 432 may be located upon axially projecting steps 439, andspaced apart in an arcuate configuration as shown. The spacing betweenthe faces of wear material 432 may be used to access bolts, etc.received in apertures 440 for coupling segment 470 with a hub component,etc. as will be readily apparent to those of skill in the art.

Referring now to FIG. 10, there is shown a sectioned view of yet anothertrack assembly 514. Track assembly 514 may include a rotatable trackengaging element 520, such as an idler or possibly a drive sprocket,configured to engage with a track having a first chain assembly 518 aand a second chain assembly 518 b, each of which includes a plurality ofinner track seals 54 a and 54 b. Track assembly 514 is an example of atrack assembly according to the present disclosure wherein rather than acontact interface which comprises a wear interface to direct wearbetween the respective components, the contact interface 540 of trackassembly 514 comprises a guide interface wherein contact betweenrotatable track engaging element 520 and track links of chain assemblies518 a and 518 b is inhibited or avoided altogether, to protect innertrack seals 54 a and 54 b. Any of the “guide” interface embodimentsdescribed herein might be used also with “wear” interfaces if desired.In one embodiment, contact interface 540 may include a first guideelement 534 on rotatable track engaging element 520, and a second guideelement 535 complementary to guide element 534 which is located on aroller bushing 525. In the embodiment shown, track engaging element 520includes a crown 534 which fits within a complementary groove 535 formedin roller bushing 525. Accordingly, during operation of track assembly514 rotatable track engaging element 520 and track chain assemblies 518a and 518 b are maintained in a state at which contact between axialsides or corners of track engaging element 520 and inboard track links524 is limited or avoided, as interaction between crown 534 and element535 tends to keep element 520 from moving laterally toward either ofchain assemblies 518 a and 518 b. In a related embodiment, theconfiguration of the components of contact interface 540 might bereversed. In other words, roller bushing 525 could include a crown, andtrack engaging element 520 could include a groove.

Turning to FIG. 11, there is shown yet another track assembly 614according to the present disclosure. Similar to the embodiment shown inFIG. 10, track assembly 614 includes a contact interface 640 wherein,rather than directing wear between components, wear is avoided byinhibiting or eliminating contact between certain of the components. Inparticular, a rotatable track engaging element 620 is provided whichincludes a tab or ridge 636 formed on an outer diameter 634 thereof. Tab636 will typically be circumferential of outer diameter 634 and may fitwithin a slot 635 formed in a roller bushing 625, such that side to sidemovement of element 620 relative to a first track chain 618 a and asecond track chain 618 b is limited, reducing or eliminating a tendencyfor rotatable track engaging element 620 to contact inner track links624 in regions adjacent inner track seals 54 a and 54 b. Contactinterface 640 might also be reversed, such that slot 635 is in element620 and tab 636 is formed on roller bushing 625.

Turning now to FIG. 12, there is shown still another track assembly 714according to the present disclosure. Track assembly 714 also includes arotatable track engaging element 720 having an outer diameter 734. Outerdiameter 734 contacts a roller bushing 725 positioned between a firstchain assembly 718 a and a second chain assembly 718 b. Track assembly714 further includes contact interfaces 740 a and 740 b. In theembodiment shown in FIG. 12, each of contact interfaces 740 a and 740 bincludes a flange 726 a and 726 b located at each end of roller bushing725. During operation, flanges 726 a and 726 b may inhibit or eliminatecontact between track engaging elements 720 and inboard track links 724in regions where track seals 54 a and 54 b are located, as flanges 726 aand 726 b are positioned inboard of track seals 54 a and 54 b andbetween links 724 and element 720. Flanges 726 a and 726 b could alsocomprise sacrificial wear material, such as hardened material, whichwears away via contact with element 720.

INDUSTRIAL APPLICABILITY

Referring to FIGS. 1-5, the portions of contact interfaces 40 a and 40 blocated on idler 20, e.g. steps 32 a and 32 b and the corresponding wearmaterial 42 a and 42 b, are generally uniform about idler 20, having agenerally circular configuration and extending inwardly from outerdiameter 34, curving into and out of the page in the FIG. 3illustration. The portions of wear interfaces 140 a and 140 b located onsprocket 68 may have an analogous configuration. The followingdescription of idler 20 in conjunction with track 16 may thus beunderstood to refer to sprocket 68, except where otherwise noted. Theportions of contact interfaces 40 a and 40 b located on links 24 a and24 b and the corresponding wear material 44 a and 44 b generally have alinear configuration, extending perpendicular to and in and out of thepage in FIG. 3. As a result, the interface between wear material 42 aand 42 b on idler 20 and wear material 44 a and 44 b is different atdifferent locations along the contact length L, given the interface of acurving component, idler 20, with straight links 24 a and 24 b.

FIG. 3 illustrates the relative location of the respective planar facesof each wear interface 40 a and 40 b at one location along contactlength L, i.e. at pin 28. Referring to FIG. 4, there is shown apartially sectioned view taken along line 4-4 of FIG. 1. FIG. 4illustrates the differing relative locations of faces 45 a and 43 a, and45 b and 43 b at a location spaced from pin 28 along contact length L.This configuration differs from that of certain earlier designs whereinat certain points along a contact length between track links and anidler, corners of the idler impinged upon surfaces of the track links inregions adjacent the track seals. As a consequence, the sharp idlercorners had a certain tendency to wear away link material more quicklythan desired, at least in certain instances. The present disclosureovercomes such wear issues by providing a different type of contactinterface altogether, with hardened material placed in differentlocations and having a different shape than that of earlier strategies.It may also be noted from FIGS. 3 and 4 that surface 97 and acounterpart surface 49 on axial side 31 each include a lower axialelevation and a lower material hardness, surface 33 and a counterpartsurface 35 on axial side 31 each include a middle axial elevation and ahigher material hardness, and surfaces 43 a and 43 b each include ahigher axial elevation and a higher material hardness. Idler 20 alsoincludes a lesser axial thickness between surfaces 97 and 49, a mediumaxial thickness between surfaces 33 and 35, and a greater axialthickness between surfaces 43 a and 43 b.

It should be appreciated that idler 20 will typically have an axialthickness between planar faces 43 a and 43 b which is slightly less thana distance between planar faces 45 a and 45 b. As a result, idler 20 mayalternately contact links 24 a and 24 b during moving track 16 intoengagement with, rotating about, and disengaging from idler 20, thealternating contact serving to guide track 16 laterally with respect toidler 20. In other words, track 16 may move back and forth relative toidler 20, resulting in alternate contact therebetween at contactinterfaces 40 a and 40 b. Relative movement of links 24 a and 24 b asthe subject portion of track 16 moves into engagement with idler 20 canalso result in sliding contact at contact interfaces 40 a and 40 b asouter diameter 34 moves toward or away from bushing 25 during engagementor disengagement, respectively, of a given portion of track 16 withidler 20. Each of these types of contact between the respective faces ofwear interfaces 40 a and 40 b can, and is intended to, wear away wearmaterial 42 a and 42 b and 44 a and 44 b. Outer diameter 34 will alsowear due to its engagement with bushing 25, often increasing the totalcontact area at interfaces 40 a and 40 b as steps 32 a and 32 b migraterelatively closer to outer diameter 34 due to loss of material fromouter diameter 34. In the case of sprocket 68, wear will take place inan analogous manner, simultaneously wearing material 44 a and 44 b fromlinks 24 a and 24 b, and wearing material 80 a and 80 b from sprocket68.

Returning to FIG. 5, it may further be noted that bushing 25 extendsinto recess 60. An end of bushing 25 within recess 60 of inboard tracklink 24 a lies in a plane A. Plane A also extends approximatelyalong/through an inboard edge of seal 54 a. Plane A is spaced fromanother plane O positioned inboard of plane A. The terms “inboard” and“outboard” as used herein in describing planes A and O will beunderstood to have meanings familiar to those skilled in the art ofmachine track, i.e. inboard means toward a center of track 16 betweenits track chain assemblies, in other words toward a longitudinalmidpoint of pin 28, whereas outboard means away from the center of track16 and toward lateral sides of track 16, in other words toward terminalends of pin 28. Plane O lies approximately at an outboard end of recess60, and is in turn spaced inboard from yet another plane B which isdefined by planar face 45 a. Planar face 143 a of nut strip 78 alsodefines a plane, plane C, which is spaced slightly inboard of plane Bbut will typically move relative thereto with side to side motion ofsprocket 68 between track chain assemblies 18 a and 18 b. FIG. 5illustrates certain of the design attributes of the present disclosurevia the illustration of planes A, B, C and O whereby seals 54 a and 54b, of each of the inboard links 24 a and 24 b of track 16 can beprotected from wear during track operation. It should be appreciatedthat idler 20 has analogous features and wear characteristics withregard to protecting seals 54 a and 54 b, as its interaction with track16 will be similar to the interaction of sprocket 68 therewith. In otherwords, the present description of planes A, B, C and O may be understoodto refer to corresponding features of idler 20.

The separation of plane A from plane O, and the separation of plane Ofrom plane B positions seal 54 a sufficiently away from wear interface140 a that any tendency for sprocket 68 to wear away link material in aregion of link 24 a adjacent seal 54 a is much reduced or eliminated ascompared with earlier designs. In other words, for link 24 a to begin towear adjacent seal 54 a, hardened wear material 44 a would need to beworn away such that planes B and O are no longer separated. Then,additional material would need to be worn away such that planes O and Aare no longer separated. The relative distances separating therespective planes may be chosen such that seal service life is not alimiting factor in track service life. The shape of the componentsdefining the wear interfaces described herein further reduces the wearrates as compared with earlier designs, as planar wear interfaces 40 a,40 b, 140 a, and 140 b may wear more slowly than interfaces whereinangled, or otherwise non-planar interfaces between components are used.Moreover, hardened material abuts and wears against hardened material atthe wear interfaces, in contrast to earlier strategies whereinunhardened material was subjected to wear.

In view of the foregoing, it will be appreciated that the uniqueconfiguration, location and composition of contact interfaces 40 a, 40b, 140 a and 140 b ensures that wearing of idler 20, sprocket 68 andtrack links 24 a and 24 b occurs in a manner that protects seals 54 aand 54 b. In other words, by selecting an appropriate shape for therelevant parts of idler 20, sprocket 68 and links 24 a and 24 b, wear oflinks 24 a and 24 b will predominantly take place in regions notadjacent to seals 54 a and 54 b. Rather, links 24 a and 24 b will have atendency to wear at planar faces 45 a and 45 b. This strategy contrastswith earlier designs, discussed above, wherein contact interfacesbetween the respective components had neither a shape nor otherattributes that specifically accounted for the location of the inboardtrack seals, and consequently wear of inboard track links from contactwith other track components had a tendency to take place in regionsclose to the inboard track seals, ultimately risking or causing sealdamage and leakage.

The embodiments of FIGS. 6 and 7 will have a tendency to operate in amanner similar to that described with regard to the embodiments of FIGS.1-5. In some instances, the embodiment of FIGS. 6 and 7 will be wellsuited to use with existing track configurations, except for relativelyminor differences. In other words, the configuration of rotatable trackengaging element 220 is such that it may be used with track chainassemblies having components sized and shaped similar to that ofexisting designs, without the need for reconfiguring link shape, length,etc. The embodiment shown in FIG. 8 has similar applicability to certainexisting track designs. With regard to the FIG. 9 embodiment, it toowill operate similarly to that of the embodiments of FIGS. 1-5, however,rather than wear occurring along a continuous contact interface, otherintermittently spaced elements of contact interface 440 will wear duringtrack assembly operation.

As discussed above, each of the embodiments of FIGS. 10 and 11 may relyat least in part upon guiding between the rotatable track engagingelement 520, 620, and the associated track chain assemblies 518 a and518 b, and 618 a and 618 b, respectively. In other words, rather thandirecting wear to particular regions of the track links, contact betweenthe respective components is limited in the first place. The embodimentof FIG. 12 can function to protect track seals 54 a and 54 b in a mannerthat relies upon both guiding between the components and sacrificialwear material. In one embodiment, flanges 726 a and 726 b may includesacrificial wear material, and rotatable track engaging element 720 mayalso include sacrificial wear material in corresponding locations.During operation of track assembly 714, wear between flanges 726 a and726 b and element 720 can prevent wear of inboard track links 724 inregions adjacent seals 54 a and 54 b. In addition, flanges 726 a and 726b may assist in guiding element 720 to reduce or eliminate the tendencyfor element 720 to contact links 724.

The present disclosure thus provides a number of different ways ofaddressing certain wear issues in track assemblies. It should beappreciated that many of the features of the various embodiments couldbe combined in a single track assembly. Moreover, many of the specificfeatures disclosed herein might be omitted from a track assembly designwithout departing from the scope of the present disclosure. It shouldfurther be appreciated that the specific geometry of the various contactinterface designs might be changed substantially. For example, ratherthan steps 32 a and 32 b having the illustrated configuration, theymight have a rounded shape. Further still, the shapes of, andinteraction between, components may vary over time as material is wornaway, while still providing protection for seals 54 a and 54 b.

The present description is for illustrative purposes only, and shouldnot be construed to narrow the breadth of the present disclosure in anyway. Thus, those skilled in the art will appreciate that variousmodifications might be made to the presently disclosed embodimentswithout departing from the full and fair scope and spirit of the presentdisclosure. Other aspects, features and advantages will be apparent uponan examination of the attached drawings and appended claims.

What is claimed is:
 1. A rotatable track engaging element, for guidingor driving a ground engaging track having first and second chainassemblies including track pins received in bores formed in inboardtrack links, bushings positioned on the track pins, and inner trackseals positioned in the bores and being adjacent to exposed seal regionsof the inboard track links facing a track guiding space, the rotatabletrack engaging element comprising: a body defining an axis of rotationand including an inner diameter surface, an outer diameter surface, andfirst and second axial sides extending from the inner diameter surfaceto the outer diameter surface, the body further having a contactinterface including seal protecting wear surfaces positioned on each ofthe axial sides; each of the axial sides includes an outboard surfaceextending a first radial distance from the corresponding seal protectingwear surface to the outer diameter surface, and an inboard surfaceextending a second, greater radial distance from the corresponding sealprotecting wear surface to the inner diameter surface; and wherein eachof the inboard surfaces includes a lower axial elevation, each of theoutboard surfaces includes a middle axial elevation, and each of theseal protecting wear surfaces includes a higher axial elevation; andwherein each of the first and second axial sides further includes anaxially protruding step, and each of the axially protruding stepsincludes, a face whereupon the seal protecting wear surface is located,disposed at a non-perpendicular face angle relative to the axis ofrotation and being formed of a sacrificial wear material, whereby thecontact interface directs contact between the body and the inboard tracklinks away from the exposed seal regions during operating the groundengaging track.
 2. The rotatable track engaging element of claim 1wherein the faces each include a conical face.
 3. The rotatable trackengaging element of claim 2 comprising an idler in which the bodyincludes a one-piece idler body, and wherein the outer diameter surfaceis positioned at a constant radial distance from the axis of rotation.4. The rotatable track engaging element of claim 3 wherein each of theoutboard surfaces adjoin the outer diameter surface at a first cornerand a second corner, respectively.
 5. A rotatable track engagingelement, for guiding or driving a ground engaging track having first andsecond chain assemblies including track pins received in bores formed ininboard track links, bushings positioned on the track pins, and innertrack seals positioned in the bores and being adjacent to exposed sealregions of the inboard track links facing a track guiding space, therotatable track engaging element comprising: a body defining an axis ofrotation and including an inner diameter surface, an outer diametersurface, and first and second axial sides extending from the innerdiameter surface to the outer diameter surface and each including a sealprotecting wear surface; each of the axial sides includes an outboardsurface extending a first radial distance from the corresponding sealprotecting wear surface to the outer diameter surface, and an inboardsurface extending a second, greater radial distance from thecorresponding seal protecting wear surface to the inner diametersurface; each of the inboard surfaces includes a lower axial elevation,each of the outboard surfaces includes a middle axial elevation, andeach of the seal protecting wear surfaces includes a higher axialelevation; and each of the first and second axial sides further includesan axially protruding step having a face whereupon the correspondingseal protecting wear surface is located, and each of the faces beingdisposed at a non-perpendicular face angle relative to the axis ofrotation, for directing contact between the body and the inboard tracklinks away from the exposed seal regions during operating the groundengaging track.
 6. The rotatable track engaging element of claim 5wherein the body includes a one-piece body.
 7. The rotatable trackengaging element of claim 6 wherein the outer diameter surface ispositioned at a constant radial distance from the axis of rotation. 8.The rotatable track engaging element of claim 7 wherein the faces eachinclude a conical face.
 9. The rotatable track engaging element of claim5 wherein each of the axially protruding steps is curved about the axisof rotation.
 10. A rotatable track engaging element for driving orguiding a ground engaging track comprising: a body defining an axis ofrotation and including an inner diameter surface, an outer diametersurface, and first and second axial sides extending from the innerdiameter surface to the outer diameter surface and each having a sealprotecting wear surface; each of the axial sides further includes anoutboard surface extending a first radial distance from thecorresponding seal protecting wear surface to the outer diametersurface, and an inboard surface extending a second, greater radialdistance from the corresponding seal protecting wear surface to theinner diameter surface; each of the inboard surfaces includes a loweraxial elevation, each of the outboard surfaces includes a middle axialelevation, and each of the seal protecting wear surfaces includes ahigher axial elevation; and each of the first and second axial sidesfurther includes an axially protruding step, for directing contactbetween the body and the ground engaging track away from exposed sealregions in inboard track links of the ground engaging track, and each ofthe axially protruding steps having a face whereupon the seal protectingwear surface is located, disposed at a non-perpendicular face anglerelative to the axis of rotation and being formed of a sacrificial wearmaterial.
 11. The rotatable track engaging element of claim 10 whereinthe body includes a one-piece body.
 12. The rotatable track engagingelement of claim 11 comprising an idler where the outer diameter surfaceis positioned at a constant radial distance from the axis of rotation.13. The rotatable track engaging element of claim 12 wherein each of theaxially protruding steps is curved about the axis of rotation.
 14. Therotatable track engaging element of claim 10 wherein each of the facesincludes a conical face.
 15. The rotatable track engaging element ofclaim 14 wherein each of the outboard surfaces defines a plane orientedsubstantially normal to the axis of rotation.
 16. The rotatable trackengaging element of claim 14 wherein each of the axially protrudingsteps extends a third radial distance between the corresponding inboardand outboard surfaces which is less than the first radial distance.